Analysis of the vapor-liquid-solid mechanism for nanowire growth and a model for this mechanism
Analysis of the vapor-liquid-solid mechanism for nanowire growth and a model for this mechanism
复制标题
DOI：
10.1021/nl072974w
复制
发表时间：
2008-05-01
期刊：
影响因子：
10.8
通讯作者：
Mohammad, S. Noor
中科院分区：
文献类型：
--
作者：
Mohammad, S. Noor
气-液-固（VLS）机制是最广泛用于生长纳米线（NW）的机制。该机制使用外来元素催化剂（FECA）来介导生长。因此，即使反应条件改变，FECA介导的液滴也不会被消耗，因此认为其非常稳定。然而，最近的实验不同，这表明，即使在最干净的生长条件下，VLS机制可能不会产生长，薄，均匀，高纯度的单晶纳米线。目前的调查已经解决了各种问题，涉及VLS增长的基本面。在解决这些问题的同时，它考虑了电，流体动力学，热力学和表面张力对NW生长的影响。它已经发现，参数，如纳米粒子种子的介观效应，FECA诱导液滴中的电荷分布，电负性的液滴相对于那些反应性纳米线蒸汽物种，生长温度，和腔室压力发挥重要作用的VLS生长。在深入分析各种问题的基础上，提出了一种简单、新颖、可延展的VLS机构模型。该模型似乎可以解释各种各样的纳米线，包括元素和化合物半导体纳米线的形成和观察到的特性。同时也提供了液滴的动力学行为对NW生长的影响的理解。这项研究发现，锥形纳米线的液滴的直径随时间的增加，主要是从逐渐掺入过量的纳米线物种FECA介导的液滴，这是由实验支持的结果。它还发现，液滴成分的最佳组合物是至关重要的VLS纳米线的生长。提出了一个近似模型来描述VLS生长的参数依赖性，该模型很好地描述了NW生长速率作为温度的函数。
The vapor-liquid-solid (VLS) mechanism is most widely employed to grow nanowires (NWs). The mechanism uses foreign element catalytic agent (FECA) to mediate the growth. Because of this, it is believed to be very stable with the FECA-mediated droplets not consumed even when reaction conditions change. Recent experiments however differ, which suggest that even under cleanest growth conditions, VLS mechanism may not produce long, thin, uniform, single-crystal nanowires of high purity. The present investigation has addressed various issues involving fundamentals of VLS growth. While addressing these issues, it has taken into consideration the influence of the electrical, hydrodynamic, thermodynamic, and surface tension effects on NW growth. It has found that parameters such as mesoscopic effects on nanoparticle seeds, charge distribution in FECA-induced droplets, electronegativity of the droplet with respect to those of reactive nanowire vapor species, growth temperature, and chamber pressure play important role in the VLS growth. On the basis of an in-depth analysis of various issues, a simple, novel, malleable (SNM) model has been presented for the VLS mechanism. The model appears to explain the formation and observed characteristics of a wide variety of nanowires, including elemental and compound semiconductor nanowires. Also it provides an understanding of the influence of the dynamic behavior of the droplets on the NW growth. This study finds that increase in diameter with time of the droplet of tapered nanowires results primarily from gradual incorporation of oversupplied nanowire species into the FECA-mediated droplet, which is supported by experiments. It finds also that optimum compositions of the droplet constituents are crucial for VLS nanowire growth. An approximate model presented to exemplify the parametric dependency of VLS growth provides good description of NW growth rate as a function of temperature.